In the automotive sector, multifunction control modules, which are produced, for example, in the form of a joystick or a rotary button, are increasingly used to control electrical or electronic systems, such as an air-conditioning system, an audio system or a navigation system.
Such modules may be associated with a display screen and allow navigation in pull-down menus which comprise various commands relating to the systems to be controlled.
However, the presence of an increasing number of complex functions brings about a multiplication of these modules. Therefore, in order to increase the ergonomic comfort, the use of an interface module with a touch-sensitive surface, in terms of a control surface or a touch screen, is considered to be an advantageous development.
When a user applies pressure to the touch-sensitive surface of such a sensor, it is possible to measure the pressure applied and/or to determine the location of the place where the pressure is applied. In this instance, pressure from the user is, for example, associated with the selection of a command.
Furthermore, in order to signal to the user that his command really has been taken into account, in particular when driving at night or in the event of blind operation, it is important for the user to have haptic feedback in order to remain concentrated on the road.
To this end, there are already known haptic feedback control modules comprising actuators, such as electromagnetic actuators, which are connected to the interface module in order to transmit a vibration movement, so that the user perceives haptic feedback informing him that his command really has been taken into account.
These electromagnetic actuators comprise a coil and one or more magnets which can be moved in translation relative to the coil. When the coil is supplied with electrical power, the magnets are caused to move, and this movement is transmitted to the touch-sensitive surface.
A second assembly, called a “voice coil” since it is associated with the loud-speakers, is obtained by assembling the movable coil in a transposed manner relative to one or more relatively fixed magnets.
However, when the movable cores arrive at the end of their travel, they strike stops or the chassis of the actuator. These repeated impacts, in addition to the undesirable noise which they produce, contribute to the wear of the components. They thus reduce the efficiency of the haptic feedback and may in the long term make it necessary to replace all or part of the actuator.
In order to overcome this problem, it is known to use damping elements between the components which are called upon to collide with each other. However, owing to their very function as damping elements, these components absorb the energy which would have been used for the movement. This absorption of energy therefore reduces the overall efficiency of the actuator.
An object of the invention is in particular to improve the efficiency, measured using the acceleration provided at the touch-sensitive surface, whilst preventing impacts between the mechanical components of the actuator.